2 * Toggles a GPIO pin to power down a device
4 * Jamie Lentin <jm@lentin.co.uk>
5 * Andrew Lunn <andrew@lunn.ch>
7 * Copyright (C) 2012 Jamie Lentin
9 * This program is free software; you can redistribute it and/or modify
10 * it under the terms of the GNU General Public License version 2 as
11 * published by the Free Software Foundation.
14 #include <linux/kernel.h>
15 #include <linux/init.h>
16 #include <linux/delay.h>
17 #include <linux/platform_device.h>
18 #include <linux/gpio/consumer.h>
19 #include <linux/of_platform.h>
20 #include <linux/module.h>
23 * Hold configuration here, cannot be more than one instance of the driver
24 * since pm_power_off itself is global.
26 static struct gpio_desc *reset_gpio;
28 static void gpio_poweroff_do_poweroff(void)
32 /* drive it active, also inactive->active edge */
33 gpiod_direction_output(reset_gpio, 1);
35 /* drive inactive, also active->inactive edge */
36 gpiod_set_value(reset_gpio, 0);
39 /* drive it active, also inactive->active edge */
40 gpiod_set_value(reset_gpio, 1);
42 /* give it some time */
48 static int gpio_poweroff_probe(struct platform_device *pdev)
52 /* If a pm_power_off function has already been added, leave it alone */
53 if (pm_power_off != NULL) {
55 "%s: pm_power_off function already registered",
60 reset_gpio = devm_gpiod_get(&pdev->dev, NULL);
61 if (IS_ERR(reset_gpio))
62 return PTR_ERR(reset_gpio);
64 input = of_property_read_bool(pdev->dev.of_node, "input");
67 if (gpiod_direction_input(reset_gpio)) {
69 "Could not set direction of reset GPIO to input\n");
73 if (gpiod_direction_output(reset_gpio, 0)) {
75 "Could not set direction of reset GPIO\n");
80 pm_power_off = &gpio_poweroff_do_poweroff;
84 static int gpio_poweroff_remove(struct platform_device *pdev)
86 if (pm_power_off == &gpio_poweroff_do_poweroff)
92 static const struct of_device_id of_gpio_poweroff_match[] = {
93 { .compatible = "gpio-poweroff", },
97 static struct platform_driver gpio_poweroff_driver = {
98 .probe = gpio_poweroff_probe,
99 .remove = gpio_poweroff_remove,
101 .name = "poweroff-gpio",
102 .owner = THIS_MODULE,
103 .of_match_table = of_gpio_poweroff_match,
107 module_platform_driver(gpio_poweroff_driver);
109 MODULE_AUTHOR("Jamie Lentin <jm@lentin.co.uk>");
110 MODULE_DESCRIPTION("GPIO poweroff driver");
111 MODULE_LICENSE("GPL v2");
112 MODULE_ALIAS("platform:poweroff-gpio");